Filament suspension



April 5, 1966 B. R.'JOHNSTON FILAMENT SUSPENSION Filed Oct. 5, 1955 INVENTOR BRUCE R. JOHNSTON 7 g, ATT EY United States Patent 3,244,928 'FILAMENT SUSPENSION Bruce R. Johnston, Huntington, W. Va., 'assignor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Filed Oct. 3, 1955, Ser. No. 537,951 6 Claims. (Cl. 313-271) This invention relates to .filamentary heated electronic discharge devices or tubes, and more particularly to the means formounting the filamenttherein.

In one use of an electronic tube, the carrier in which the tube is mounted is subjected to terrific accelerations of the order of 27,000 g thereby placing parts within a tube under terrific stresses even where the parts are very light when weighed under normal gravitational forces.

In an effort to maintain the filament in proper relationship to other electrodes in the'discharge device when subjected to heat elongation and to violent forces, spring support constructions were evolved such as are shown in the patents to Kelley, 2,467,390, and Sassaman et al., 2,506,895. These devices provided for spring loaded filaments with tabs at each of opposite ends of the tube to support the filament, one of the tabs being crimped about and welded to the filament and further welded to the movable portion of the spring support for the filament. However, it was found in practice that in the use to which these discharge devices were put, the filament broke at the tab much too frequently.

It is an object of this invention to provide a structure whereby breakage of filament due to shock forces will be minimized.

It is a further object of the invention to provide a construction whereby the weak point of the filament at the top anchorage is eliminated.

It is a still further object of the invention to reduce the live weight or weight subject to movement on violent tube displacement, in the direction of length of the filament, to reduce the inertia of the filament between its spring support and the other end of the filament, to thereby efiect less yielding of the support and therefore less snap back action of the spring on the filament.

It has also been found in practice, that there is considerable difiiculty in effecting a weld between the tab on the spring end of the filament and the spring since the parts in which such construction is used are usually small and the filament and spring are very fine and delicate. It is therefore still another object of this invention to avoid this difficulty by making the weld to more substantial structure than to the spring but still maintain tension of the spring on the filament.

These and further objects will be apparent after reading the following specification and claims in conjunction with the accompanying drawing in which:

FIG. 1 is a side elevational view of a tube embodying the filament suspension of the invention, the glass envelope being partially broken away.

FIG. 2 is a perspective view of the top portion of the electrode mount turned about 90 clockwise from the position shown in FIG. 1.

FIG. 3 is a diagrammatic representation of the location of the electrodes and their supports.

Referring to the drawings with greater particularity, at there is shown a fragmentary portion of a glass enclosure, the same constituting a glass bulb and having a lead supporting wafer at the bottom, the bulb and wafer being sealed together, as is conventional in the art. Sealed into the wafer are a number of support rods designated as 12, 14, 16, 18, 20, 22 and 24, the rods 12, 18, and 22 continuing through the bottom of the wafer and serving as external connections to the various electrodes within the tube. Within the tube there .is a .pair of insulating spacer elements 26 and 28 through which all of the rods are threaded and between which are located the grid 30 and anode 32 of the tube. Since the invention does not concern itself with the specific character of these elements, further description of them is unnecessary. The spacers, side rods and electrode are held together by any of the methods conventionally employed in the art as by placing straps, notshown, around certain of the rods above the top insulating wafer and below the bottom wafer and abutting the wafers, and by making the grid and anode of a size to extend from one wafer to the other.

Welded to one of the rods 18 near spacer 26 is :support bar 40, this bar extending across the intersection of the major and minor axes 'of the grid 30, i.e., across the longitudinal axis of symmetry of the grid. To this .bar is welded a tab 42 of folded over material between the folds of which by friction and welding is held the filamentary cathode 44, stripped of its coating at the portion confined within the tab.

It has been customary in the past to attach this wire to the free end of a cantilever spring, as shown in the Kelley and Sassaman et al. patents previously referred to, in order to maintain the filament under tension so that when heated and it elongates it shall not sag and short against the closely nearby grid. The fastening of the filament to the spring was effected by equipping the upper uncoated end of the filament with a tab and welding this tab to the free end of the spring. However, such construction tended to weaken the joint since welding affected the material deleteriously. When the tube is subjected to large gravitational forces, the weakened area would give way rendering the tube useless. Moreover, in the prior constructions, on subjection of the tube to the accelerations of high gravity, the inertia effect of the mass of the tab, since it is suspended from the free end of the spring, would greatly increase the forces tending to rupture the filament.

With applicants construction, the weight of the tab is removed from the moving part of the system and the strain on the filament is reduced by passing a bare portion of the wire slidably over the spring, over a fixed portion and onto a non-movable support within the tube.

As in the prior art, applicants tube is provided with a metallic wing 50 suitably supported, as by welding the same onto the metallic rod 12. This wing has a narrow neck portion 52 with an end turned over on its self as at 53 to rigidly support a bar 54 about which is wound the conductive spring 56, with the two ends coiled about the rod and extending on to be welded to the wing as at 58. Its cantilever end extends substantially horizontally beyond the longitudinal center of the grid and terminates in a V with a downwardly extending offset 60 at the tip of the V. The filament 44 is threaded through an opening 62 in the upper insulator, and then over the spring with the filament lying slidably in the offset 60 and then continuing on over the bent over portion 53 and down alongside the back of the wing. Here the filament has welded thereto a second tab 64, similar to the tab 42, and this tab is welded to the wing. The spring of course, is placed under tension prior to Welding the tab 64 in place. By this means the strain on the filament due to any downward pull along the length of the filament is distributed along the whole length of the filament from tab to tab and the weight of the tab is removed from the moving part of the filamentary system when the filament and spring move in response to centrifugal forces.

Having thus disclosed the invention, what is claimed is:

1. In an electron discharge device, a filament suspension comprising a fixed filament support at one end of the device to which one end of the filament is secured,

a cantilever p g securedwithin the device with the filament trained over the free end of the spring and fastened to the second fixed support, the spring being under stress when the filament is in place.

2. In an electron discharge device, a filament suspension comprising a fixed filament support to which one end of the filament is secured, a second fixed support, a cantilever spring secured to the second support with the filament trained over the free end of the spring and fastened to the second fixed support, the spring being under stress when the filament is in place.

3. In an electron discharge device, a filament suspension comprising a fixed filament support to which one end of the filament is secured, a second fixed support, a V-shaped wire cantilever spring having its free ends secured to the second support and having a dip in the apex of the spring, a filament fastened to the first support, trained over the spring and fastened at its other end to the second support with the filament lying in the dip in the wire and with the spring under flexure.

4. In an electron discharge device, a filament guide and suspension comprising a fixed support at one end of the device, an apertured insulated spacer spaced from the support, a filament traversing the discharge device, fastened to said support and threaded through said aperture, a second support at the other end of said device, a cantilever spring under flexure extending from said second support and beyond the aperture in the spacer, a filament guiding depression in the free end of the spring, the otherwise free end of the filament passing from the aperture in the spacer over the spring with the filament lying in the depression in the spring and continuing on to the second support and fastened thereto.

5. In an electron discharge device, a filament guide and suspension comprising a fixed support at one end of the device, an apertured insulated spacer spaced from the support, a filament traversing the discharge device, fastened to said support and threaded through said aperture, a second support at the other end of said device, a cantilever spring under flexure extending from said second support and beyond the aperture in the spacer, a filament guiding depression in the free end of the spring, the otherwise free end of the filament passing from the aperture in the spacer over the spring with the filament lying in the depression in the spring and continuing on to the second support, a tab secured to the otherwise free end of the filament, said tab being fixed to the second support.

6 In anelectron discharge device, a filament suspension for a single run filament, stationary means at one end of the device for fastening one end of the single run filament, stationary means at the other end of the device for fastening the other end of the single run filament and a tcnsioned spring fixed within the device reacting against the filament and applying tension to the filament.

References Cited by the Examiner UNITED STATES PATENTS 1,926,128 9/1933 Van Steenis 313278 2,100,306 11/1937 McCarthy 313-278 2,467,390 4/1949 Kelly 313272 X 2,672,570 3/ 1954 Carlstrom 313278 2,728,017 12/1955 Haas 313-278 JOHN W. HUCKERT, Primary Examiner.

NORMAN H. EVANS, KATHLEEN H. CLAFFY, Examiners. 

1. IN AN ELECTRON DISCHARGE DEVICE, A FILAMENT SUSPENSION COMPRISING A FIXED FILAMENT SUPPORT AT ONE END OF THE DEVICE TO WHICH ONE END OF THE FILAMENT IS SECURED, A SECOND FIXED SUPPORT AT THE OPPOSITE END OF THE DEVICE, A CANTILEVER SPRING WITHIN THE DEVICE WITH THE FILAMENT TRAINED OVER THE FREE END OF THE SPRING AND FASTENED TO THE SECOND FIXED SUPPORT, THE SPRING BEING UNDER STRESS WHEN THE FILAMENT IS IN PLACE. 